The girls were the ones who had agency during that quest, and they were the ones planning and acting to public shame each other. The MC just picks one side to help in the dispute because either option would help him towards his listed objective at the moment: gain access to the VIP area. MC just does what he does in every quest: manipulates people and environment to achieve the current goal
I like the girls having agency or things happening without MC control but the problem is what options MC has to react to those events instead and 0.18 options seem pretty inconsistent with how he acted previously: In past events MC always had an option to
do the dirty work personally. Offering an option for MC entering the showers with Victoria (even consensually now that she can be so submissive) or an option for MC proposing Victoria to deceive the other girls and "pretend to be a victim as well" with an "incidental" threesome with MC or even some option to deceive them all into "accidentally" enter in the showers for a lesbian threesome (and in those two last options again a choice to share or not the video) would be as manipulative and effective for his objective, but also proactive and consistent with that specific personality you offered in old events. How the guy that decided to go the gloryhole with Victoria, persuade Brooke that groping her was a good option to enhance the fake video, convince Chloe to have sex as fake boyfriend to trick the security guy, etc, could become so apathetic to just allow Victoria (the newly "submissive" Victoria, not less) to be fucked by the fat guy or follow Victoria orders and betray the other girls publicly shaming them (passively), instead trying a personal dirty work route as in every other past event?
I can't grasp the concept of "sharing" a woman you don't have a romantic interest with
That's very odd to me, honestly. Exclusivity, rarity, individual control, privacy and many other attractive elements of that kind of "I will do it personally" MC route can be all purely sexually focused preferences in real life lacking any romantic involvement, pretty common ones I would say.
I suggested before how all this is more obvious in games with darker settings than LiS, as the erotic rpg focused on slavery I mentioned in a previous comment in which fans still avoid all "sharing content", including selling any slave, despite how wild is the world and despite many of them enjoy the most sadistic and degradant actions with slaves. Those players lack any "romantic interest" in those simple fucktoy slave npcs without any deep personality, but they prefer the personal and private approach yet.
Ps. I still like this game a lot, I have followed its entire development and helped a bit as one of its patrons. I say all this as a fan disappointed with that specific choice, not as a casual hater.